title of the thesis - Department of Geology - Queen's University

preferentially oriented fracture planes but fracture orientations do not conform to mine-scale shear
zone orientations. Macroseismic event focal mechanisms are inconsistent and fault plane
solutions do not have coherent nodal planes or pressure and tension axes. A stress inversion of P-
and T-axes from microseismic events on the 7400 Level indicates that mine-scale stress
orientations are consistent with far-field stresses.
An anomalous cluster of microseismic and macroseismic events, referred to as Cluster 1 in this
thesis, exhibits unusual seismic event parameter values and stress inversion results. Influences
external to the 7400 Level, including mining of the Plum Orebody and 461 Orebody, may create a
complex stress environment, complicating analysis of the 7400 Level.
Numerical modelling of stress on the 7400 Level shows that stress flows around the excavation,
forming a ring of high stress. In this two-dimensional analysis, there is little deflection in stress
trajectories in proximity to faults. This suggests that faults are strong and brittle. High stresses
align parallel to SW-striking structures to the south of the excavation, lowering stresses to the
southwest. Comparison of modelling results with seismicity shows an agreement between areas
of high stress and areas of dense seismicity, as well as between areas of low modelled stress and
areas of little to no seismicity. Numerical models that allow for non-recoverable deformation
show yielding around the excavation and along SW-striking shear zones and both elastic and
plastic models demonstrate slip along the Plum Shear Zone and often along the Return Air Raise
Shear Zone in proximity to the excavation, though this occurs where the rockmass has yielded.
5.2 Conclusions
Given that large-magnitude events require large slip surfaces, it would be expected that mine-scale
shear zones would provide the area necessary to produce macroseismic events in the Creighton
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